“What we can say is that the real driving force behind [the Maine cases] was the local police department. They’ve asked us not to identify them and we are respecting that,” he said.

According to Reuters, the FBI arrested 150 people across the United States on charges of holding children against their will for prostitution, a three-day weekend sweep that officials on Monday called the largest-ever operation against child sex trafficking.

The suspects, whom the FBI referred to as “pimps,” were arrested in 76 U.S. cities and are expected to face state and federal charges related to sex crimes and human trafficking, FBI and U.S. Justice Department officials said at a news conference, Reuters reported on Monday.

The news agency said that FBI agents and local police recovered 105 children during the operation at truck stops, motels, casinos and other places where they were forced to work as prostitutes.

The FBI said the suspects were not part of the same operation. It said some belonged to organized crime while others acted alone. The bureau did not immediately release a list of the suspects.

The FBI typically does not investigate adult prostitution, leaving it as a state and local matter, but in recent years it has made child prostitution a priority in a program the FBI calls Operation Cross Country. The program includes highway billboards asking people to call the FBI with tips.

About 1,350 people have been convicted as part of the program and at least 10 of them were sentenced to life in prison, officials said.

The latest sweep was the seventh and largest under Operation Cross Country, they said.